Ride your bike to work when you have a newborn? You selfish bastard!
Seriously, I have 2 young kids and my bicycle commuting habits are not even on my wife's radar. She knows it makes me happy, reduces my stress and keeps me healthy. I mean, it's not like you are hanging out at the bar with the guys on a nightly basis. Well, if you are, THAT might have to change a little.
Also, be prepared for those that tell you that you are being irresponsible for commuting via bicycle when you have kids. I have a co-worker who occasionally reminds me about my "dangerous lifestyle".